The present invention generally relates to an apparatus for aiding a hearing function difficulty due to an aging effect and the like. More specifically, the present invention relates to a digital acoustic signal processing apparatus for improving voice articulation.
Conventionally, it has mainly used an analog type hearing aid to process an amplitude and a frequency characteristic of a voice with employment of an analog circuit to aid difficulty in hearing. On the other hand, very recently, in the held of the hearing aids for aiding declined hearing ability, it has been developed digital hearing aids with application of digital signal processing to aid difficulty in hearing. With respect to this research and development trends, one of examples is disclosed in "The Topics of Hearing Aid" of A Journal of the Acoustical Society of Japan, volume 45, No. 7, 1989, pages 549 to 555. The acoustic signal processing method employed in the digital hearing aid is described in "Digital Hearing Aid Emphasizing Speech Characteristics" of A Journal of the Acoustical Society of Japan, volume 43, No. 5, 1987, pages 356 to 361. The method for aiding hearing ability by way of a hearing aid into which an audio output from a television receiver or the like is inputted, has been described in JP-A-1-179599.